Batteries, such as electrochemical batteries are known devices for storing energy for high energy density applications, greater than 10 Watt hours per kilogram (Wh/kg), for example.
Capacitors, such as supercapacitors and ultracapacitors, are used for storing energy for applications having energy density requirements less than 10 Watt hours per kilogram (Wh/kg), particularly if a power density greater than 1000 Watts per kilogram (W/kg) is required.
Batteries are not capable of achieving power densities of supercapacitors. Supercapacitors are not capable of achieving energy densities of batteries.
The technologies for packaging and providing electrical contacts on batteries and capacitors, including supercapacitors and ultracapacitors are well known. However, limitations in materials available prevent known storage devices from having both high energy densities and high power densities at the same time.
U.S. Pat. Publ. No. 2010/0008021 A1, published Jan. 14, 2010, discloses a porous carbon electrode with conductive polymer, referred to as a polyaniline electrode, useful in fabricating supercapacitors. This reference includes a background on various types of supercapacitors and the limitations of the materials used in supercapacitors.